A semiconductor device having a semiconductor chip such as an IC chip with an electrode for soldering and a base such as a heat sink and a lead frame is disclosed in Japanese Patent Application Publication No. 2003-110064. In the device, the semiconductor chip is bonded to the base through the electrode by using a solder. The device is manufactured in such a manner that a mounting surface of the semiconductor chip for soldering is grinded and cleaned, and then the electrode is formed on the mounting surface of the chip. After that, the solder is inserted between the semiconductor chip and the base, and the solder is heated up equal to or higher than the solidus temperature of the solder so that the solder is reflowed. Thus, the chip is soldered to the base with the solder so that the chip is electrically, thermally and mechanically bonded to the base.
However, in the device, a solder portion between the chip and the base may include a void. The void causes a contact area of the solder portion to decrease so that electric resistance of the solder portion becomes larger. Thus, heat generation at the solder portion is increased.
Further, the heat generated in the chip is radiated to the outside of the device through the base such as a lead frame. When the void is formed in the solder portion, the heat radiation efficiency of the device is reduced. Furthermore, since the contact area of the solder portion is reduced, the mechanical strength of bonding between the chip and the base is decreased. Thus, the chip may be removed from the base.
Therefore, it is required to reduce the void in the solder portion.